This man's admitted to an attempt to con the ref that's very tacky (8)
I believe the answer is:
adhesive
'tacky' is the definition.
(I've seen this in another clue)
'this man's admitted to an attempt to' is the wordplay.
'this man's' becomes 'hes' (he refers to a man).
'admitted to' indicates putting letters inside.
'an' becomes 'a'.
'attempt to' becomes 'dive' (I can't justify this - if you can you should believe this answer much more).
'a'+'dive'='adive'
'hes' put within 'adive' is 'ADHESIVE'.
'con the ref that's very' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for adhesive that I've seen before include "What a sticker" , "Sticky; glue" , "Stuff that sticks" , "Glue, gum" , "Hide vase (anag)" .)